1. Technical Field of the Invention
The embodiments of the invention relate to wireless communications and, more particularly, to location positioning using wireless LAN technology.
2. Description of Related Art
Various communication devices utilize global positioning systems to determine accurate location of the device. Global Navigation Satellite Systems (GNSS) are the most well known systems in use today. Such GNSS systems include the Global Positioning System (GPS) in the United States, Galileo in the European Union and GLONASS in Russia. As illustrated in FIG. 1, GNSS systems rely on a plurality of satellites to triangulate the location. As shown in FIG. 1, a vehicle receives coordinated signals from a number of satellites and determines the timing of the arrival of the signals to triangulate the position.
Although GNSS systems may provide accurate positioning at the receiver end, the satellite communication link is line-of-sight, so that performance is compromised when the mobile receiver is indoors or in crowded urban environments (urban canyons). Accordingly, GNSS systems may not provide the desired performance to identify the location of the device, when significant obstruction exists between the positioning satellites and the device to triangulate the location of the device.
A different type of positioning system uses the wireless local area network (WLAN) technology to provide positioning information. WLAN-based positioning systems emerged as a way to augment GNSS in environments where satellite reception is problematic. However, WLAN-based systems are local and not global. FIG. 2 shows an example of a WLAN-based system that triangulates the position of a receiver. FIG. 2 illustrates a mobile person, who is in possession of the receiver. As shown in FIG. 2, three WiFi access points (APs) generate respective beacons with each's own identifier. That is, the mobile person can receive the beacons from the surrounding WiFi APs without requiring association. The receiver, by measuring the received signal strength from each AP, is able to estimate an approximate distance from each AP to triangulate its position, when the user accesses a database that stores a list of measured signal strengths.
Although WiFi signals need not be line-of-sight, WiFi signals are impacted by multipath radio frequency (RF) propagation and other interferences encountered in the channel between a particular AP and the receiver. Increasing the density of the access points by utilizing more APs for triangulation improves the precision, but adds significant investment in equipment and infrastructure.
Accordingly, for a WLAN-based positioning system, there is a need for having a more robust scheme in which positioning may be determined.